The ultimate long-term objectives of this project are to fully describe and quantify the extent of chemosensory dysfunction in the elderly, to understand its etiology, to identify in the chemical senses any mechanisms which may be common to aging of other sensory systems, and to elucidate the relationship between chemosensory function and nutritional status in the elderly. Studies conducted during the current grant period have established the critical need for longitudinal data on chemosensory aging as well as raised a number of provocative questions which have never been posed before. Thus the specific aims of the current proposal are 1) to conduct a longitudinal study of chemosensory aging to assess the rates of decline in chemosensory functions, assessed at different levels of the systems, and to examine rates of decline across chemosensory modalities; and 2) to conduct a highly-related series of cross-sectional studies which will investigate nasal pathology in olfactory dysfunction of Alzheimer's disease, probe for the existence of olfactory dysfunction in adult patients with Down's syndrome, and compare Weber Ratios (WRs) for olfactory, trigeminal, and gustatory stimuli in young and elderly subjects. Subjects in these studies will be active, non-institutionalized adults with no hospitalizations in the year preceding testing. They will be drawn from four age groups: young adults, middle-aged adults, the elderly and the oldest-old. Among these subjects will be a group of elderly patients with senile dementia of the Alzheimer's type and a group of adults with Down's syndrome. A multi-faceted approach, employing both classical and modern psychophysical techniques, will be used to assess chemosensory function: two-alternative, forced-choice threshold methods; determination of Weber Ratios; magnitude matching of intensity; and bipolar line-scaling of hedonics. Nasal airway resistance will be measured by anterior rhinomanometry. Nasal disease will be assessed by ear, nose and throat examinations, including endoscopy and nasal cytology. A more complete understanding of chemosensory function in the elderly may suggest methods for maximizing taste and smell perception, food palatability, and, hence, dietary intake and nutritional status in the geriatric population. These studies will not only aid in enhancing the quality of life for aging populations, but will also increase our understanding of basic sensory processes.